Sweet Potatoes May Have Originated In India

Based on the discovery of 57-million-year-old leaf fossils, scientists in India and the US suggest that the sweet potato first appeared in India.

AsianScientist (Jun. 1, 2018) – Sweet potatoes may have originated in Asia, contrary to earlier findings which suggested that they first appeared in America. These findings have been published in the Proceedings of the National Academy of Sciences.

Sweet potatoes may be a staple at Thanksgiving dinners in the US, but scientists have long debated the origins of the tubers. In this study, researchers led by Professor David Dilcher at Indiana University, in collaboration with colleagues in India, identified 57-milion-year-old leaf fossils from eastern India as being from the morning glory family, which includes sweet potatoes and many other plants.

Dilcher’s collaborators, Dr. Gaurav Srivastava and Dr. Rakesh C. Mehrotra of India’s Birbal Sahni Institute of Palaeosciences, discovered the fossils in Meghalaya, a state in northeastern India. The team then used microscopic analysis of the shape and structure of the leaves, comparing details of the leaf veins and cells with plants in the genus Ipomoea, which includes sweet potato but also hundreds of other plants. Using such analysis to examine evolutionary relationships has been a hallmark of Dilcher’s paleobotany research career.

Their findings suggest that the predecessors of the sweet potato plant originated in the late Paleocene epoch in the East Gondwana land mass that became part of Asia. This is in contrast to previous fossil evidence which suggested that the morning glory family may have originated in North America about 35 million years ago.

The researchers also found that the morning glory family, which the sweet potato plant belongs to, and the nightshade family, which includes potatoes and tomatoes, diverged earlier than previously thought. Together with the recent, separate discovery of 52-million-year-old nightshade fossils in Argentina, these findings indicate that morning glories developed in the East and nightshades in the West.

“I think this will change people’s ideas,” said Dilcher. “It will be a data point that is picked up and used in other work where researchers are trying to find the time of the evolution of major groups of flowering plants.”

The article can be found at: Srivastava et al. (2018) Paleocene Ipomoea (Convolvulaceae) from India with implications for an East Gondwana origin of Convolvulaceae.


Source: Indiana University; Photo: Pixabay.
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